1. Technical Field
The present invention relates to a wiring substrate including a through wiring passing through a substrate, a MEMS device including the wiring substrate, a liquid ejecting head including the wiring substrate, and a liquid ejecting apparatus which is provided with the liquid ejecting head.
2. Related Art
A micro electro mechanical system (MEMS) device which is a representative of a liquid ejecting head is provided with a wiring substrate on which a surface wiring is connected to a through wiring provided in a through hole. As such a wiring substrate, a wiring substrate on which a through hole is formed on a substrate, and a through wiring is formed in the through hole has been proposed (for example, refer to JP-A-2000-52550).
However, there is a difference of a linear expansion coefficient between the through wiring and the wiring substrate, and thus the through wiring may be deviated from the through hole due to a temperature change. There is a concern that due to the deviation of the through wiring, the surface wiring may be disconnected.
In addition, in the wiring substrate used in a MEMS sensor such as an ultrasonic sensor which is an example of the MEMS device, the through wiring becomes a part of the wiring through which a minute current generated by driving of a piezoelectric element flows. In such a wiring substrate, if the loss resistance of the through wiring is large, there is a concern that it becomes difficult to detect a minute current.